A variety of spaceborne and/or airborne instruments have been applied to spatio-angularly sample and image atmospheric radiance.
These include the Multiangle Imaging SpectroRadiometer (MISR) disclosed in Multi-angle Imaging Spectro-radiometer (MISR) Instrument Description and Experiment Overview, IEEE Trans. Geoscience and Remote Sens. 36 (1998) 1072-1087, and Atmospheric Transmittance from Spacecraft Using Multiple View Angle Imagery, Appl. Opt. 24 (1985)3503-3511; Airborne Multiangle SpectroPolarimetric Imager (AirMSPI) disclosed in Dual-photoelastic-Modulator-Based Polarimetric Imaging Remote Sensing, Appl. Opt. 46 (2007) 8428-8445, and First Results from a Dual Photoelastic-Modulator-Based Polarimetric Camera, Appl. Opt. 49 (2010) 2929; and POLDER disclosed in Polarimetric Remote Sensing of Ocean Waves, In:Proc. MTS/IEEE OCEANS (2009) 1-5, An Analytical Model for the Cloud-Free Atmosphere/Ocean System Reflectance. Remote Sensing of Environment 43 (1993) 179-192, and The Compact High Resolution Imaging spectrometer (CHRIS): The Future of Hypersepctral Satellite Sensors. Imagery of Oostende Coastal and Inland Waters, In:Proc. Airborne Imaging Spectroscopy Workshop (2004).
However, these imaging architectures have a spatial resolution of several kilometers per pixel, an angular resolution of approximately 7 angles per view, and their orbit requires several days to return to the same terrestrial spot. Furthermore, spaceborne instruments are extremely expensive and unscalable.
Thus, existing sky-imaging systems rely on expensive, high quality cameras and components. Due to their complexity and cost, they typically provide an estimate cloud-base mapping over narrow regions above a narrow-baseline camera pair.
Other systems for providing a three-dimensional (3D) mapping of cloud-tops include satellite-based MISR which may take several minutes to capture multiple viewpoints of a region, during which the clouds may move. Weather radars that are used to sense raindrops, which are much larger than cloud-drops and ice crystals, do not sense clouds that do not produce rain. The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the figures.